Sure Start Runs Then Surges

How's the compression? Does it change much once the engine warms up? Is your fuel clean? Have you tried different fuel? Even the tiniest bit of floatsam can cause problems. It sounds like you are already doing this, but pull the backplate off and make sure everything is in order - reed and retainer clean and intact, unobstructed venturi, and a good seal between the crankcase.

Have you taken it apart? If not take it apart, clean it in fuel, replace anything needed. Check your fuel line to be sure it's not flopping around in the tank and it has a spring. After you seat the reed be sure the clip is in correctly and the reed spins. As a rule of thumb spending some time doing preventive maintenance will save you time and aggravation in the long run.

Matt pretty much put everything in a nutshell Compression in the Estes surestarts can sometimes be an issue It may feel ok before its first run but as it warms up and wears in, the P/C set lost compression and would cause inconsistent runs and hard starting. This is due to Estes at the time did not put much time and effort in properly fitting the Piston/Cylinder sets upon assembly, the crankcase sets also suffered problems too like the for mentioned aluminum chips in the crankcase which required the engine to be disassembled and cleaned out before its first run. They also have sealing issues and the reeds can sometimes be problematic. Pop the plastic reed retainer off and check to make sure the steel reed has no burs or other things that could keep it from seating properly against the face of the venturi and check the face of the venturi for anything that can cause an airleak (blowby) Perform the suck and blow test to make sure it's seating properly (should act like a one-way valve). Also check for congealed oil and other debris in the nipple and jet and as mentioned by Matt and others make sure the fuel that's getting to the engine is clean. hope this helps man (Bandit)

Ok, thanks for the help, and I will try to answer the best I can.

@robot797 - No I did not clean out the engine before I used it as it was a used engine that had just not been run in a few years. I had however disassembled it to make sure everything was there and intact. It was not a new Sure Start.

@microflitedude - Compression appears to be fine. As for warming up then having problems, I would say that that would be a good guess, as the problems arose after 8-10cc of fuel. Sig Champion 25% nitro. My othe Cox engines ran on the same fuel with no problems. No I have not tried different fuel. I also have a quart of Sig Champion 15% nitro. I will disassemble the engine later tonight or tomorrow to check that everything is in order.

@jsesere - Yes and no. Taken apart for a quick visual before starting it up, but not back apart since the bench run. I will give it a good cleaning if time permits and no other problems are visible after disassembly tonight or tomorrow. I will check the reed retainer as well as that the reed spins when all is assembled.

@TDbandit - As for a Cox or Estes Sure Start, I could not verify which it was made by. I had acquired it say around 07-08 I believe and it was run and had sat for a while before that as it was a bit stiff then from sitting. It did appear to have good compression both before, during, and now. I will look for any filings in the crankcase when it is disassembled. Will also do a thorough check on the reed and venturi assembly. Will also get my tip cleaners and go through the fuel nipple and jet for foreign debris.

In 2007 Estes was liquidating the last of their Cox stock after a steady decline in quality control. Estes simply stopped caring. You'll hear horror stories of mismatched and mislabeled engines cobbled together from leftover parts, even .051 pistons being forcefully rammed into .049 cylinders.

Most Surestarts are fine though, and will give you good numbers once you sort out the insides. Mine has been a reliable runner and swings a 5x3 safety tip around 14.5K on 25%. They use a dual bypass, dual boost flute cylinder like TeeDees. They do however lack SPI and have slotted exhaust.

Let us know if you find anything. I'd go ahead and slap on a new glowplug/head gasket and eliminate them as a possibility.

Ok. Back from the dungeon. So I took it apart. Crankcase is clean, gasket ok. Took the backplate apart. It had a wire e-clip and a clear reed in it. They both appeared fine. Took a look and the brass tube in the back behind the reed looked 'green'. So I pushed a wooden skewer and rag in the hole and rotated a few times. It came out a bit greener than when it went in. I then shone a flashlight through the needle hole through the fuel nipple and saw a greenish color. So I took a pin and pushed it through all the way. A tiny piece of gunk came out, and now the light was visible through the tube. I hooked up a piece of line to the fuel nipple and proceeded to blow through it as I lightly poked the hole from behind the reed. I now had a nice airflow. So, I reassembled the reed and retainer. I was able to blow through with little resistance, and was also able to suck back with resistance. The reed rotates freely under the clip. I then assembled the engine, needle and all. Hooked up the fuel line again, and now I am not able to blow through again, but at the 4 1/2 turns out, I can get a bit with a lot of pressure. I will try to run it tomorrow evening, but may be busy. I may try a floppy disc reed also.

"I'd go ahead and slap on a new glowplug/head gasket and eliminate them as a possibility. "

I would like to, but do not have another glowhead or spare gaskets around here. I may try making another from a pop can as before. And I forgot to mention a minute ago, compression is really good.

NEW222 wrote:It had a wire e-clip and a clear reed in it.

If that's the case, I don't think we're talking about a true Surestart here. I don't believe Surestarts ever used a wire clip, only a plastic retainer. Regardless, it sounds like you're on the right track getting rid of the green gunk. I'd suggest that you soak the backplate assembly in some fuel or alcohol overnight with the needle removed, then flush fuel through the spray bar with a syringe.
re-install the needle a couple of turns (wide open) and flush again to clean the spray hole.
Sounds like goo is your problem.

Rod.

I agree with Rod, I don't recall any SureStarts coming with the wire clip. What color is the back plate? You might have an LD made product engine either way, everything is the same as far as cleaning and maintenance. (Bandit)

One item I didn't see mentioned is to check the crankcase back to ensure that it is flat so there is no leakage.

George

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@TDbandit - Black backplate, grey choke tube. It was used prior to me coning into possession of it, and I would like to say that I had acquired it a few years ago and it was stiff even back then.

@gcb - You did not see it mentioned, but last night after disassembly, I did however put it down on 500 grit paper on a solid surface and made a few passes as it appeard to have slightly raised edges around the screw mounting holes.

@Mudhen - you seem to understand me correctly. I did notice a dark colored 'fluid' at a crankcase joint while running. As to exact location, I cannot remember as I did not pay too close of attention at it at the time, just that yes, I did notice it and I dismissed it as gunk and the such from after sitting these many years.

Thank you all again for the help and advice given, and I will heed and follow it as I have time and tend to my engine. I will post updates as I go along. I may even run it again tomorrow just to see if and where I saw the dark fluid.

If it makes a difference, it has a #3 cylinder with the dual slit exhaust.  Just putting everything out there. After looking at the MH-Aerotools (?) website, it looks like a product engine without the muffler and a grey choke tube installed. Just a guess after mentioning Surestart.

NEW222 wrote:If it makes a difference, it has a #3 cylinder with the dual slit exhaust.  Just putting everything out there.  After looking at the MH-Aerotools (?) website, it looks like a product engine without the muffler and a grey choke tube installed.  Just a guess after mentioning Surestart.

Yup sounds like a Leisure Dynamics era cox product engine with the surestart snorkel installed interesting, didn't know the surestart snorkel would fit the older engines. (Bandit)

I'm pretty sure the wire e-clip means the backplate pre-dates the Surestart, so probably from a product engine. I think you can make a snorkel fit one of those.

Surging can be the reed floating. It can also mean an air leak between the backplate and the crankcase. You already decked it on a flat sandpaper, but sometimes the screws bottom out where the threads weren't cut deep enough into some of the 4 holes, and it feels like the backplate is snugged up when it really isn't. I have had to grind a half millimeter or more off the tips of the screws to tighten it enough. Or an additional crankcase gasket might seal it. but it never has for me. The best fix is to get a 2-56 bottoming tap and extend the threads deeper into the hole. The hole is plenty deep enough to add 4 or 5 more turns on the screw this way and it stops those leaks.

If you decide to shorten the screws, put a nut on it first. Then you can use it to straighten the leader threads as you remove it, making the screw much easier to start without cross threading it.A dremel cutoff wheel males less of a mess of the tip of the screw than a grinder. After cutting with a dremel, I usually bump the tip with the face of the cutoff wheel to clean it too.

Before I realized it was the screw holes, I used Permatex successfully after setting for a day, but it looks like crap and makes a mess to clean up when you take it apart again.
Rusty

Ok, here are a couple of pictures. I today had made a stainless steel and floppy disc reed and tried both out. This is now weird. They both fit, rotate freely with the clip installed, as well as the original in the picture. So I hook up a fuel line and do the blow/suck test. I can pull and push air through without much resistance. Then I realize I have to put the needle in. So I reinstall the needle into the backplate. Try again. Now there is restriction both ways, and the needle is 4 turns out as well. I am at a loss now, as I cannot blow air through it even. Hope this little description helps a bit more, along with the pictures. Thank you all again.

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Should also note that there is a D on the left side of the backplate, and a C on the right. This is as seen in the picture.

Are you aware that the "blow/suck" test should be through the air intake? Sounds like you might have been blowing through the spray bar. Fit a larger diameter hose over the air intake (without the choke tube & removed from engine) and you should be able to blow but not suck.

Rod.

Also make sure the needle valve in in all the way and seated or it will draw air in through the nipple while performing the "suck" side of the test and give a false reading. (Bandit)

Oldenginerod wrote:Are you aware that the "blow/suck" test should be through the air intake?  Sounds like you might have been blowing through the spray bar.  Fit a larger diameter hose over the air intake (without the choke tube & removed from engine) and you should be able to blow but not suck.

Rod.

Well, I am aware now. Yes, I was using the fuel nipple on the bottom. Damn, I feel like an idiot.

Don't need no stinkin tube, wrap lips around reed side of backplate and lightly blow.
Reminds me of a Bogie movie.

crankbndr wrote:Don't need no stinkin tube, wrap lips around reed side of backplate and lightly blow.
Reminds me of a Bogie movie.

That's what I was gonna say!In that arrangement, it should flow freely when you suck and not flow AT ALL when you blow... regardless of the needle setting.

crankbndr wrote:Don't need no stinkin tube, wrap lips around reed side of backplate and lightly blow.
Reminds me of a Bogie movie.

Works on tanks too.
Bob